Electromagnetic relay

ABSTRACT

The relay comprises a base body ( 27 ), a coil ( 1 ), a core arrangement ( 3 ), an armature ( 10 ) and a contact system. The contact spring ( 16 ) is configured as an arc and arranged to be connected with the armature ( 10 ) in such a way that it is subjected to uniform, low mechanical loading. As a result a material can be used for the contact spring ( 16 ) which presents high electrical conductivity, so that the forward resistance of the relay is reduced. The contact spring ( 16 ) and armature ( 10 ) are arranged in such a way that a relay with a compact structure can be obtained.

FIELD OF THE INVENTION

The present invention relates to a universally applicableelectromagnetic relay.

BACKGROUND OF THE INVENTION

A relay contact spring must generally accomplish two tasks. On the onehand it supports a switch contact, which is pressed against a fixedcontact via the spring force of the contact spring, on the other hand itis via said contact spring that the current is conducted to the switchcontact. Whereas in the first case mechanical loading ability is ofsignificance, the second task requires high electrical conductivity.Materials which exhibit high flexural strength in order to resist highmechanical loading, however, exhibit low conductivity and vice versa. Ifthe relay is to generate large currents, the forward resistance isgenerally too great due to the poor conductivity of the contact springand an additional flex must be provided to conduct the current to themovable contact.

A simpler method to reduce forward resistance of a relay is either todesign the spring as particularly wide or to use a material exhibitinggood conductivity. The latter variation, however, requires themechanical loading of the spring to be relatively minor. The spring canbe arched to this effect in order to uniformly distribute the ensuingbending stress.

A relay comprising an arched leaf spring is already known from DE 36 40737 C2. Said spring is fixed at one end to a magnet yoke and at theother end to a plane side of the armature. A projection of said leafspring supports a switch contact. Mechanical loading of the springmaterial is significantly higher in the region close to the fasteningsthan it is in the middle of the spring. Consequently, an arched shape ofthis type is suitable only in as far as it enables, through lowmechanical loading of the spring material, the use of a material withhigh electrical conductivity.

SUMMARY OF THE INVENTION

It is the aim of the present invention to provide an electromagneticrelay with a low forward resistance without the need for additionalcomponents or an increase in structure size.

According to the invention, this aim is realised by a relay featuringthe following characteristics:

a base body,

a coil,

a core arrangement,

an armature, which at one armature end is pivotally arranged around anarmature rotational axis to an end section of the core arrangement andthe other end of which forms a free armature end,

at least one fixed contact,

a contact spring, which is attached at one fastening end to an immovablesection of the relay, comprising a movable contact spring end, which iscoupled to the free armature end, and comprising at least one switchcontact, which cooperates with at least one of the fixed contacts,whereby the contact spring is generally overall arched and designed as amomentum spring and whereby the switch contact is arranged at a middlesection of the contact spring.

The relay according to the invention is advantageous due to themechanical loading of the contact spring being very low and uniform.This is achieved primarily through designing the contact spring as amomentum spring. A momentum spring can be defined in that both springends are attached to third parts in such a way that no rotation of thespring end takes place to each third part around the fastening point.

Due to the movement of the free armature end, a torque is applied to thecontact spring. Both spring ends are fastened in a torque-resistantmanner.

The contact spring has the characteristic feature that the deformationof the spring during movement occurs in such a way that bendingmodification is almost constant. On this basis, the bending loads of thecontact spring are, to a large extent, constant along the spring. Themechanical loadings of the spring are also low due to the large lengthof the contact spring. This is the case when the free contact spring endis fastened to the free armature end.

The low loading in the region of the contact spring ends is ensured inan advantageous manner in that the fastening plane of the movablecontact spring end lies tangential to the moving direction of the freearmature end, since as a result the spring is merely incidentally bentat the fastening point. There is equally an advantage when the fasteningplane of the fastening end is essentially perpendicular to a very shortconnecting line extending from a fastening edge, on which the movablepart of the contact spring commences, to the armature rotational axis.

The forward resistance is furthermore reduced, if the switch contact isarranged in a middle region of the contact spring, since as a result thecurrent path is shortened from a linking connector to the switchcontact. This arrangement has the additional advantage that a pathtransformation occurs from the free armature end to the switch contactand the contact opening forces of the switch contact are increased incomparison to an arrangement close to or beyond the armature end. Incombination with an armature comprising a particularly large openingangle and thus covering a large path when closing, a weaker design ofthe magnet system is possible, at the same supporting a compactstructure. As a result, an even weaker material can in addition be usedfor the contact spring, since the required restoring force is lower.

A particularly advantageous embodiment describes the contact spring inthe form of an elliptical section, as in this embodiment the loading isdistributed particularly uniformly over the length of the contactspring.

A further advantage follows from the armature rotational axis beingpositioned in approximately the middle of the region described by thecontact spring, since as a result the free armature end is guided on acircular path, which subjects the contact spring to a particularlygentle stress, as a homogenous loading distribution ensues for thecontact spring. The following applies for a substantially arched spring:if the form of the spring approaches that of an arc, the arc's centralpoint would correspond to the rotational axis.

An additional advantage of the invention follows from the contact springbeing simultaneously able to bias the armature into a resting position,thus dispensing with an armature restoring spring.

The production of a contact spring for a relay according to theinvention is particularly straightforward if the contact spring exhibitsa constant width over its entire length and if for instance boreholescan be allotted at particular points for alleviating the load of thecontact spring.

The contact spring is preferably made out of a highly electricallyconductive material, the mechanical characteristics of which arenevertheless sufficient on the basis of the uniformly low mechanicalloadings.

Further details of the embodiments of the invention are described in thesubclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail in the form of an embodimentshown in the drawings. In the drawings:

FIG. 1 represents a relay according to the invention, with the contactspring also acting as a restoring spring.

FIG. 2 represents a partial view showing the armature and the contactsystem of the relay of FIG. 1, and

FIG. 3 represents a further embodiment of a relay according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a first embodiment according to FIGS. 1 and 2, a coil 1 is positionedon a first leg of a core arrangement 3, such that an armature bearingsection 4 of the first leg, otherwise not visible in the figures, islocated outside the coil 1. A pole section 5 of a second leg 6 of thecore arrangement 3 forms a core pole face 7, which cooperates with anarmature pole face 8 at a free end 9 of an armature 10. On the edge ofthe armature bearing section 4 opposite the second leg 6, the armature10 is pivotally mounted with an inside edge around a bearing edge 11,which forms the armature rotational axis, such that in an opened state awedge-shaped armature bearing gap 12 is formed between the armature 10and the armature bearing section 8 and disappears in an armature closingposition. The inside edge arises from the formation of two projections20 to the armature 10. The armature 10 is essentially L-shaped andarranged in such a way that the oblique leg of the L, representing thefree armature end 9, points outwards. The armature 10 deviates from theL shape to the extent that in a middle section 14 it is bent inwards.

The free armature end 9, with its armature pole face 8 and the core poleface 7, forms a working air gap 15. In the region of its front end 8 ain the closing direction, the armature pole face 8 is essentiallyperpendicular to a connecting line extending to the bearing edge 11.When the armature 10 is attracted, the core pole face 7 extendsapproximately parallel to the armature pole face 8. Due to theintegrally formed projections 20 the armature 10 is unable to move, dueto the magnet force operating in the working air gap 15, such that theworking air gap 15 closes. A contact spring 16 has among others the taskof pressing the inside edge of the armature 10 against the bearing edge11 of the end section 4, so that the armature 10 is capable merely of arotary movement.

The opening angle of the armature bearing gap 12 of such a magnetsystem, for instance when 10°, is large in comparison to a conventionalflap armature system with an opening angle generally no greater than 5°.

A fastening end 17 of the contact spring 16 is fastened together with alinking connector (not represented) to the armature bearing section 4 atthe side on which the bearing edge 11 is also located, close to a coilformer flange 13, preferably by injection moulding. In the region of itsfastening end 17, the contact spring 16 tangentially approaches a planewhich lies parallel to the front face of the armature bearing section 4.

A very short connecting line 18 between a clamping edge 19, on which thefastening end 17 of the contact spring 16 and a movable part 21 of thecontact spring 16 are adjacent, and the bearing edge 11, standsapproximately perpendicular on the fastening plane of the fastening end17. This ensures that the loading of the contact spring 16 at theclamping edge 19 is similarly high to other regions of the contactspring 16. There is the possibility, however, that in other embodiments,this criterion is not fulfilled to the same extent, if for instanceconstructive measures for the sake of saving space result in a differentposition of the fastening edge.

The movable part 21 of the contact spring 16 is bent around the armaturebearing section 4 and a longitudinal leg 22 of the armature 10 and isfastened to the free armature end 9. The movable end 23 of the contactspring 16 follows the free armature end 9 in its movement. In the regionof its fastening to the armature 10, the contact spring 16 lies in aplane which runs tangentially to the direction of movement of the freearmature end 9. Due to this arrangement, the contact spring 16 adoptsthe approximate form of an ellipse, whereby approximately a quarter ofthe ellipse remains open. The fastening of the contact spring to thearmature could also ensue through a movable coupling. To optimise thesize of the relay, the contact spring 16 can also be designed in such away that the shape deviates strongly from an ellipse.

Through the arrangement of the contact surface 16, the bearing edge 11lies approximately in the middle of the ellipse, resulting during themovement of the armature in a “natural” loading of the contact spring16, which distributes itself uniformly over the entire length of thecontact spring 16.

The contact spring 16 comprises a middle section 24, on which a switchcontact 25 is fastened. In the embodiment represented in FIGS. 1 and 2,said switch contact cooperates with a fixed contact 26, the position ofwhich is fixed on a base body 27. The switch contact 25 lies onapproximately half of the contact spring length, resulting in a shortcurrent path to the linking connector (not represented) at the fasteningend 17 of the contact spring 16. The opening forces for the opening ofthe contacts 25 and 26 are particularly large, since force transmissiontakes place between the free armature end 9 and the switch contact 25.The distance of the contacts 25 and 26 in the opening position isnevertheless sufficient, as the opening angle of the armature bearinggap 12 can be selected to be correspondingly large. On the basis of theadvantageous embodiment of the armature 10, there are nevertheless nodisadvantages in terms of the efficiency of the magnetic circuit.

During the activation of the coil 1, the armature pole face 8 isattracted to the core pole face 7, and the armature 10 moves into theclosing position. When the armature 10 is in the closed position, themovable contact 25 forms a connection with the fixed contact 26.

When the coil 1 is deactivated, the contact spring 16, which in aparticularly advantageous arrangement also acts as a restoring spring,moves the armature 10 in the direction of the opened position, as thearmature 10 is biased in the opened position during the resting state ofthe relay. It is also conceivable, however, to put in an additionalrestoring spring. The opening movement of the armature 10 causes thecontacts 25 and 26 to separate, and the current path through the relayis interrupted.

A design of the contact spring according to the invention, according tothe embodiment shown in FIGS. 1 and 2, is also advantageous in that forthe uniform loading of the spring, the spring width does not need to bealtered and no other measures, for instance load-alleviating boreholes,are necessary, as is normally the case. As a result, manufacturing isrendered easier, which also brings about advantages from a costperspective.

In a further embodiment according to FIG. 3, a relay according to theinvention is shown in a concrete embodiment. Similarly to the schematicrepresentation of FIGS. 1 and 2, the relay comprises no additionalarmature restoring spring, instead the armature restoring force, whichbiases the armature 35 into an opening position, is ensured by thecontact spring 30. It is also possible, however, to design the relaywith an additional armature restoring spring; the latter can forinstance be arranged in the free region between the armature 35 and thecontact spring 30.

In the middle region of the contact spring 30 a movable contact 32 isarranged, which, in the opened position of the armature 35, cooperateswith a first fixed contact 33, and in the closed armature position witha second fixed contact 34.

The shape of the contact spring 30 deviates from the shape of thecontact spring 16 of the first embodiment and through several bendingedges of the contact spring 30 ensures a space-saving structure.

In addition to the represented embodiment with a single contact thecontacts 32, 33 and 34 can also be designed as double contacts. In thiscase, however, a longitudinal slot would have to be provided in thecontact spring 30 between both switch contacts, to level out theinevitable tolerances at the level of the contacts. With such a designof the contacts, the contact system can also be connected as a bridging(double) change-over. In this case the current supply to the switchcontacts would have to occur separately to the spring tensioning.

We claim:
 1. An electromagnetic relay comprising: a base body; a coil; acore arrangement; an armature, which at one armature end is pivotallyarranged around a rotational axis to an armature bearing section of thecore arrangement and the other end of which forms a free armature end;at least one fixed contact, and; a contact spring, which is attached atone fastening end to an immovable section of the relay, comprising amovable contact spring end, which is coupled to the free armature end,and comprising at least one switch contact, which cooperates with atleast one of the fixed contacts, whereby the contact spring is generallyoverall arched and designed as a momentum spring, and whereby the switchcontact is arranged at a middle section of the contact spring.
 2. Therelay according to claim 1, wherein the armature rotational axis ispositioned in approximately the middle of the region described by thecontact spring.
 3. The relay according to claim 1, wherein the fasteningplane of the movable contact spring end lies tangential to the directionof movement of the free armature end.
 4. The relay according to claim 1,wherein the fastening plane of the fastening end of the contact springis essentially perpendicular to a very short connecting line extendingfrom a fastening edge, on which the movable part of the contact springcommences, to the armature rotational axis.
 5. Relay according to claim1, wherein the movable contact spring end is movably coupled to the freearmature end.
 6. The relay according to claim 1, wherein the contactspring simultaneously biases the armature into a resting position. 7.The relay according to claim 1, wherein at the armature in the region ofthe armature rotational axis at least one projection is formed, which isadjacent to the armature bearing section, whereby a shifting of thearmature in the direction of the free armature end is avoided.
 8. Therelay according to claim 1, wherein the armature rotational axis isfixed through a bearing edge to the armature bearing section of the corearrangement and a thereto adjacent inside edge of the armature.
 9. Therelay according to claim 8, wherein the contact spring presses theinside edge of the armature against the bearing edge.
 10. The relayaccording to claim 1, wherein the contact spring is made out of a highlyelectrically conductive material.
 11. The relay according to claim 1,wherein an additional restoring spring biases the armature into aresting position.
 12. The relay according to claim 1, wherein thecontact spring essentially describes an elliptical section.
 13. Therelay according to claim 1, wherein the contact spring exhibits auniform width over its length, at least between the fastening end andthe switch contact.
 14. The relay according to claim 1, wherein anopening angle between the armature and the armature bearing section ofthe core arrangement lies between 5° and 15°.
 15. The relay according toclaim 1, wherein the switch contact and the fixed contacts are designedas double contacts.
 16. The relay according to claim 15, wherein thecontact spring comprises a longitudinal slit in the middle sectionbetween both contacts.
 17. The relay according to claim 1, wherein thearmature pole face, in the region of its front end in the closingdirection, is essentially perpendicular to a connecting line to thearmature rotational axis and in that when the armature is attracted, thecore pole face extends at least approximately parallel to the armaturepole face.